Class 8 Maths Worksheet: Algebraic Identities
The method (Split into easy parts): (a + b)² = a² + 2ab + b². (a − b)² = a² − 2ab + b². (a + b)(a − b) = a² − b²; so a² − b² = (a + b)(a − b). a² + b² = (a + b)² − 2ab = (a − b)² + 2ab.
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- 1.If a + b = 5 and ab = 6, what is a² + b²?
- 2.Use (a + b)² = a² + 2ab + b² to find 41².
- 3.Use a² − b² = (a + b)(a − b) to find 51² − 21².
- 4.Use (a + b)² = a² + 2ab + b² to find 42².
- 5.If a − b = 5 and ab = 24, what is a² + b²?
- 6.Use (a + b)(a − b) = a² − b² to find 72 × 68.
- 7.Find the value of x² − 2xy + y² when x = 9 and y = 6.
- 8.Use (a + b)² = a² + 2ab + b² to find 74².
- 9.Use a² − b² = (a + b)(a − b) to find 73² − 23².
- 10.Use (a + b)(a − b) = a² − b² to find 101 × 99.
- 11.Find the value of x² + 2xy + y² when x = 7 and y = 6.
- 12.Use (a + b)² = a² + 2ab + b² to find 86².
- 13.Find the value of x² − 2xy + y² when x = 6 and y = 5.
- 14.Use a² − b² = (a + b)(a − b) to find 20² − 9².
- 15.Use a² − b² = (a + b)(a − b) to find 68² − 62².
- 16.Use (a + b)² = a² + 2ab + b² to find 26².
- 17.Use (a + b)² = a² + 2ab + b² to find 62².
- 18.Use (a − b)² = a² − 2ab + b² to find 83².
- 19.Use a² − b² = (a + b)(a − b) to find 83² − 44².
- 20.Use (a − b)² = a² − 2ab + b² to find 95².
- 21.Use (a + b)² = a² + 2ab + b² to find 92².
- 22.If a + b = 9 and ab = 18, what is a² + b²?
- 23.Use a² − b² = (a + b)(a − b) to find 68² − 24².
- 24.Use a² − b² = (a + b)(a − b) to find 36² − 7².
- 25.If a − b = 3 and ab = 28, what is a² + b²?
- 26.Use a² − b² = (a + b)(a − b) to find 41² − 28².
- 27.Find the value of x² − y² when x = 5 and y = 1.
- 28.If a + b = 7 and ab = 6, what is a² + b²?
- 29.Use (a + b)² = a² + 2ab + b² to find 11².
- 30.Use (a + b)(a − b) = a² − b² to find 93 × 87.
- 31.Use (a + b)² = a² + 2ab + b² to find 12².
- 32.Use a² − b² = (a + b)(a − b) to find 96² − 43².
- 33.Use a² − b² = (a + b)(a − b) to find 52² − 6².
- 34.Use (a − b)² = a² − 2ab + b² to find 51².
- 35.Use (a + b)² = a² + 2ab + b² to find 51².
- 36.Use (a + b)(a − b) = a² − b² to find 29 × 11.
- 37.Find the value of x² + 2xy + y² when x = 3 and y = 2.
- 38.Use (a + b)² = a² + 2ab + b² to find 19².
- 39.Use (a − b)² = a² − 2ab + b² to find 74².
- 40.Use (a + b)² = a² + 2ab + b² to find 57².
Answer key
- 13
- 1681
- 2160
- 1764
- 73
- 4896
- 9
- 5476
- 4800
- 9999
- 169
- 7396
- 1
- 319
- 780
- 676
- 3844
- 6889
- 4953
- 9025
- 8464
- 45
- 4048
- 1247
- 65
- 897
- 24
- 37
- 121
- 8091
- 144
- 7367
- 2668
- 2601
- 2601
- 319
- 25
- 361
- 5476
- 3249
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